The following line on page 110 of Pro ASP.NET MVC Framework does not make sense to me:
string links = ((HtmlHelper)null).PageLinks(2, 3, i => "Page" + i);
I don't understand what is the null
doing in the above statement?
I was unable to do .. HtmlHelper.PageLinks(....)
Is the Page开发者_如何学GoLinks Method an extension method?
It's invoking an extension method on a null "instance" of an HtmlHelper. Probably there's no HtmlHelper in scope and the author can't be bothered to create one. The PageLinks
method itself will not require a reference to an HtmlHelper, so effectively the author is passing null
.
If you think about the signature of the extension method:
public static string PageLinks
(this HtmlHelper helper, int val1, int val2, Func<someType,string> func)
It simply means that the parameter helper will be passed as null
. It's a weird construct though, particularly in a book. It's got a really hacky smell to it.
The call could be restated (perhaps more clearly) as:
AuthorsHtmlExtensionsClass.PageLinks(null, 2, 3, i => "Page" + i)
Just reading though my MVC2 copy of the same book, (it's the end of the SportsStore application, right?), Steven has changed the code to:
HtmlHelper html=null;
...
html.PageLinks(...)
Which I suppose is a little clearer.
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